Buttermilk. It's a secret ingredient. Soak the meat in buttermilk for a couple of hours, dredge in a standard fry batter (flour, egg, bread crumb) and fry in your cast iron. Season well with salt and pepper. You can crank up your batter with cayenne or more subtlely with herbs.

But the creamy gravy is equally essential and that's a flour/roux based sauce.

I worked in the business office of a truck stop on I-55 outside of Chicago in the 80s, had my youngest son, then asked (begged) for any job on the restaurant side in the 90s. Best job ever, until the owner sold it and everything went from homemade to heat-and-serve, except the eggs and toast. So sad.

CFS (waitress shorthand)

Measure flour into a large shallow bowl or glass baking dish: For every cup of flour, add 1 1/2 teaspoons table salt, 1/4 teaspoon pepper and a pinch of cayenne or hot paprika, if desired. Use a fork to mix spices into the flour. For four steaks, you'll probably need 2 cups.

In another shallow bowl, beat together one egg, a half-teaspoon of baking powder, a half-teaspoon of baking soda and a cup of buttermilk.

Gently but firmly pound cube steaks to a little less than half an inch thick. (You can use round steak or a cut of chuck if you want, but hammer them until they're 1/4" thick--they'll seize up and become thicker during cooking.)

Lightly sprinkle each side of each steak with additional salt and pepper. Press a steak into the flour mixture, making sure to get the flour into all the nooks and crannies on both its sides, and shake off the excess flour, then dip the steak into the egg mixture, turn it and allow the excess to drip off. Coat the steak with flour again and place it on a wire rack. Repeat until all steaks are coated. Allow to dry about 15 minutes before frying Do not discard the coating mixtures--you will use them in the gravy.

Heat 1/2" to 3/4" of oil (vegetable, soybean, corn, peanut are great with cast iron, but I try to stay away from canola in cast iron--just my preference) in a large cast iron or heavy stainless steel skillet over medium-high heat to 375 degrees. Slip two to four steaks gently into the oil; they should have a finger-width between them, so fry them in batches if they don't fit comfortably in the pan. Fry, turning once, until dark golden on both sides, about 5 minutes. Transfer the steaks to the paper towel-lined plate to drain for only half a minute, then transfer them to a wire rack. Place in a 200 degree F oven while frying the remaining steaks and/or making the gravy.

When all the steaks have been fried and are being kept warm in the oven, turn off the heat and carefully ladle or spoon all but 2 or 3 tablespoons of the hot oil into a heatproof container and allow it to cool before discarding or storing it for another use. Turn the heat to medium and stir in 2 or 3 tablespoons of the flour mixture and stir until the flour has absorbed the oil. Whisk in 2 or 3 cups of liquid (most of us like a 50-50 mix of buttermilk and whole milk or all milk, but one daughter-in-law swears by milk and chicken broth), along with the buttermilk/egg mix, scraping up the browned bits off the bottom of the pan.Cook and stir until until thickened (gravy should be slightly thin--it will thicken up as it cools) and bubbly and the raw flour taste is gone. Whisk in some salt and pepper, if needed.

Betteirene has nailed it. I would add the key is in technique -- you need the skillet and the oil HOT, and don't TOUCH that steak for four or five minutes. If you try to fool with it before then, the breading will come off. It'll stick initially, but "turn loose" when it gets brown. That's where I always failed, until I learned a little patience...